Lighting circuit load calculator

Use this page when a lighting row needs to become a traceable electrical load before it is entered into a circuit schedule, estimate, switchboard worksheet or maximum-demand review. The calculator is deliberately narrow: it adds fitting watts, applies an entered allowance, divides the row into equal groups and estimates current from the entered voltage and power factor.

The useful record is not "lighting allowed for". A stronger record says, for example, "LTG-1, 12 fittings at 18 W, 10% allowance, 230 V, PF 0.90, one group, 1.15 A per group". That row can then be checked against the circuit schedule, grouping plan, voltage-drop review, controls arrangement and product data.

Field use cases

This page is most useful before the lighting row is copied into another document. Once a vague value is buried in a schedule, it becomes hard to tell whether the number came from product data, an allowance, a rounded estimate or a design change.

Lighting load data checklist

If the luminaire schedule is provisional, keep the calculator record provisional as well. Changing from a nominated luminaire to another driver, wattage or power factor can change the current even when the physical fitting count stays the same.

Circuit grouping matrix

Grouping is a record decision, not a design approval. A group current can look acceptable while the actual installation still needs switching, emergency lighting, cable route, voltage-drop, protection and controls review.

Review current matrix

The review current is not supplied by this page. It is an entered project comparison value. This keeps the calculator transparent and avoids turning a simplified worksheet into a circuit-design rule.

Review workflow

1. Identify the lighting row or area from the drawing, luminaire schedule, takeoff or quote.
2. Confirm whether the row should be single phase or a balanced three-phase group.
3. Enter the luminaire quantity and watts per fitting from the current product or schedule basis.
4. Enter any driver, ballast, control gear or project allowance used for the load row.
5. Enter the number of equal circuit groups represented by the row.
6. Confirm the voltage and power factor used for current conversion.
7. Enter a review current only when the project has a comparison value to use.
8. Read connected load, adjusted load and current per group together.
9. Carry the row into maximum demand, voltage drop, circuit schedule or estimating work as required.
10. Stop before treating the result as lux design, cable sizing, protection selection or compliance approval.

This sequence keeps the lighting load calculation in its proper role. The row is a current estimate and record aid. It is not a substitute for the decisions that come after the row is known.

Worked records

These examples show why the record should not be reduced to a watts-to-amps conversion. Quantity, allowance, phase basis and grouping can each change the current that is carried into the next document.

Using the result in actual work

The result usually leaves the calculator as one row in a larger document. In an estimate, the connected load can support a variation note when luminaire counts change. In a circuit schedule, the group current helps the reviewer see whether rows have been split as intended. In a maximum-demand worksheet, the adjusted lighting row should sit beside other loads without pretending to be the whole installation result.

Good lighting load records make later checking easier. They show the load basis before someone starts debating cable size, voltage drop, switching zones or maximum demand.

Boundary with neighbouring calculations

Keeping this boundary clear protects the value of the page. The calculator gives a transparent lighting load and current row. It does not pretend to design the lighting installation.

Australian context

Australian lighting load planning normally sits inside a 230/400 V, 50 Hz installation context, but the final use of the result depends on the project. Current Australian standards, local authority requirements, project specifications, product data, controls requirements and manufacturer instructions can govern the final design.

This page does not reproduce controlled standards content and does not publish fixed circuit ratings. It records arithmetic from the values entered by the user so the lighting row can be reviewed in the proper electrical documents.

Stop points

• The luminaire count is not confirmed from a luminaire schedule, drawing or takeoff.
• The watts per fitting are taken from a marketing description rather than electrical product data.
• The allowance is copied without a project or manufacturer basis.
• Mixed fitting types are averaged into one row without review.
• A balanced three-phase basis is selected for a row that is not actually balanced.
• The result is used for cable sizing, protective-device selection or voltage drop without the relevant downstream checks.
• The result is treated as lighting design, lux compliance or emergency-lighting verification.
• Current standards, project specifications, local authority requirements or manufacturer instructions are being treated as optional.